Silicone composition which can be crosslinked into an elastomer by hydrosilylation in the presence of carbene-based metal catalysts, and catalysts of this type

ABSTRACT

This invention relates to silicone compositions which can be crosslinked, preferably into elastomers, by hydrosilylation of at least one PolyOrganoSiloxane -A- carrying unsaturated bonds, using at least one polyorganohydrosiloxane —B— in the presence of a carbene-based metal catalyst —C— as defined in the description and which optionally comprises at least one inhibitor -D- of the hydrosilylation reaction.

The invention relates to the catalysis of hydrosilylation reactions ofethylenically and/or acetylenically unsaturated compounds (for example,olefins or acetylenic derivatives), in particular those involvingpolyorganosiloxanes (POSs) carrying Si—H units and POSs carryingSi-(ethylenic or acetylenic unsaturation) units.

More specifically, the invention relates to silicone compositions whichcan be crosslinked (preferably into elastomers) by hydrosilylation of atleast one PolyOrganoSiloxane -A- (POS) carrying unsaturated bonds usingat least one polyorganohydrosiloxane —B— in the presence of a metalcatalyst —C— and which optionally comprise at least one inhibitor -D- ofthe hydrosilylation reaction.

Hydrosilylation reactions which make it possible for silicones tocrosslink are conventionally catalysed by platinum catalysts (U.S. Pat.No. 2,823,218, U.S. Pat. No. 2,970,150). In practice, to date, themajority of industrial hydrosilylation reactions are catalysed by theKarstedt solution, which is composed of platinum complexes in which theplatinum is in the 0 oxidation state.

The very high catalytic activity of this type of catalyst, even atambient temperature, is a major disadvantage in the context of its usein polyaddition HCEs as the crosslinking of the elastomer begins as soonas all the components are brought into contact.

The document WO 01/42558 discloses in particular metal complexes of useas hydrosilylation catalysts, of formula:

in which:

R₃ represents a hydrogen atom; a (C₁-C₈)alkyl group; or a(C₃-C₈)cycloalkyl group;

T₁ and T₂ are identical and represent (C₁-C₈)alkyl or (C₃-C₈)cycloalkyl;

R_(d) and R_(e) are identical and represent (C₁-C₈)alkyl or (C₃-C₈)cycloalkyl.

According to this application, the catalysts are employed for thecatalysis of the reaction of a compound comprising an unsaturated bondwith a compound exhibiting at least one ≡S—H unit.

Patent U.S. Pat. No. 5,728,839 itself also discloses metal/carbenecomplexes with heterocyclic carbenes; they are described as being ableto be of use as catalysts for the hydrogenation or hydroformylation ofunsaturated organic compounds. There is no mention of the crosslinkingof silicones in this document.

In point of fact, it might be advantageous to have available, in thefield of crosslinkable silicones (in particular those which can becrosslinked into elastomers), catalysts which are active under hotconditions and inactive or virtually inactive at ambient temperature.This would make it possible to formulate single-component siliconecompositions which can be crosslinked under hot conditions and which arestable on storage for lengthy periods of time at ambient temperature(pot life). Single-component silicone compositions are those whichcomprise, in the same mixture, all the reactive entities (Si-VinylPOS/Si-H POS) and the catalyst. Conventionally, crosslinking inhibitorsare used to increase the pot life of single-component siliconecompositions. Thus, with the Karstedt catalyst, the use of an inhibitoris essential and makes it possible to change, for example, the stabilityat ambient temperature of an Si-Vinyl POS/Si-H POS composition from 1min to 24 H.

Objectives

In such a state of the art, one of the essential objectives of theinvention is to provide a silicone composition which can be crosslinkedby hydrosilylation and which comprises, as catalyst, one or more metalcomplexes based on heterocyclic carbenes, this catalyst having a lowactivity at ambient temperature, so as to make possible the preparationof single-component compositions comprising the catalyst and compoundscapable of reacting under hot conditions by hydrosilylation ofunsaturated units, while being stable at ambient temperature for lengthyperiods (e.g. 1 d to a few months).

Another essential objective of the invention is to provide a siliconecomposition which can be crosslinked by hydrosilylation and whichcomprises, as catalyst, one or more metal complexes based onheterocyclic carbenes, this composition not being the site, duringcrosslinking, of isomerization side reactions or of colorations capableof interfering with the hydrosilylation.

Another essential objective of the invention is to provide novel metalcomplexes based on heterocyclic carbenes which can be used ashydrosilylation catalysts, the latter having to be highly active underhot conditions and inactive or virtually inactive at ambienttemperature, so as to be able to formulate single-component siliconecompositions which can be crosslinked under hot conditions and which arestable on storage for lengthy periods of time at ambient temperature(pot life), this being achieved with little or no crosslinkinginhibitor.

Another essential objective of the invention is to provide ahydrosilylation process and in particular a process for thehydrosilylation of ethylenically and/or acetylenically unsaturatedcompounds in the presence of a catalyst comprising the novel metalcomplexes targeted above.

These objectives are achieved by the present invention, which relates,first, to a silicone composition which can be crosslinked byhydrosilylation of at least one PolyOrganoSiloxane -A- (POS) carryingunsaturated bonds (example: ethylenic and/or acetylenic unsaturation(s)]using at least one polyorganohydro-siloxane —B— in the presence of ametal catalyst —C— and which optionally comprises at least one inhibitor-D- of the hydrosilylation reaction;

-   -   characterized in that the catalyst —C— comprises at least one        compound selected from the products of formula (I):        in which:    -   M represents a metal chosen from the metals of Group 8 of the        Periodic Table as published in the Handbook of Chemistry and        Physics, 65th edition, 1984-1985;    -   L_(γ) represents a carbene of formula (II):        in which:    -   A and B, which are identical or different, represent C or N, it        being understood that, when A represents N, then T₄ does not        represent anything and, when B represents N, then T₃ does not        represent anything;    -   T₃ and T₄ independently represent a hydrogen atom; an alkyl        group; a cycloalkyl group optionally substituted by alkyl or        alkoxy; an aryl group optionally substituted by alkyl or alkoxy;        an alkenyl group; an alkynyl group; or an arylalkyl group in        which the aryl part is optionally substituted by alkyl or        alkoxy; or else    -   T₃ and T₄ can together and with A and B, when the latter each        represent a carbon atom, form an aryl;    -   T₁ and T₂ independently represent an alkyl group; an alkyl group        optionally substituted by alkyl; a perfluorinated alkyl group or        an alkyl group optionally substituted by a perfluoroalkyl group;        a cycloalkyl group optionally substituted by alkyl or alkoxy; an        aryl group optionally substituted by alkyl or alkoxy; an alkenyl        group; an alkynyl group; or an arylalkyl group in which the aryl        part is optionally substituted by alkyl or alkoxy; or else    -   T₁ and T₂ independently represent a monovalent radical of        following formula (V):        V₁-V₂   (V), in which:        -   V₁ is a divalent hydrocarbonaceous radical, preferably an            alkylene,        -   V₂ is a monovalent radical chosen from the group of the            following substituents:            -   alkoxy, —OR^(o) with R^(o) corresponding to hydrogen,                alkyl or aryl,            -   amine, preferably N(R^(o))₂ with R^(o) corresponding to                hydrogen, alkyl or aryl;    -   T₁ and T₂ independently represent a monovalent radical of        following formula (W):        W₁-ω-W₂   (W)        -   in which:        -   W₁ is a divalent hydrocarbonaceous radical, preferably a            linear or branched C₁-C₁₀ alkylene, which is optionally            substituted;        -   ω represents:            —R¹C═CR¹—        -   with R¹ corresponding to H or alkyl,        -   or            —C≡C—;        -   W₂ is a monovalent radical chosen from the group of the            following substituents:        -   R²=alkyl or H;        -   Si-alkyl or Si-alkoxy, preferably —Si(R³)₃ with R³=alkyl;        -   alcohol, preferably —C(R⁴)₂OH with R⁴═H or alkyl;        -   ketone, preferably            with R⁵=alkyl;        -   carboxyl, preferably            with R⁶=alkyl;        -   amide, preferably            with R⁷═H or alkyl;        -   acyl, preferably            with R⁸=alkyl;        -   or else    -   the substituents T₁, T₂, T₃ and T₄ can form in pairs, when they        are situated at two adjacent points in the formula (II), a        saturated or unsaturated hydrocarbonaceous chain;    -   and with the condition that at least one substituent T₁ and/or        T₂, which are identical or different, represent(s) a monovalent        radical of following formula (V):        Z₁-Z₂   (V)        -   in which:        -   Z₁ is a divalent hydrocarbonaceous radical, preferably an            alkylene,        -   Z₂ is a monovalent radical chosen from:            -   a (C₅-C₃₀)cycloalkyl radical comprising at least one                heteroatom in the ring, preferably nitrogen,            -   a (C₆-C₃₀)aryl radical comprising at least one                heteroatom in the aromatic ring, preferably nitrogen,    -   L_(α) and L_(β) are ligands which are identical to or different        from one another and    -   each represent:    -   with, in these formulae (III.1) and (III.2):    -   Z¹, Z², Z³, Z⁴, Z⁵ and Z⁶    -   each independently representing:    -   a. hydrogen,    -   b. a halogen,    -   c. a cyano,    -   d. a saturated or unsaturated, electron-withdrawing or        non-electron-withdrawing, hydrocarbonaceous group, preferably        unsaturated adjacent to the double or triple bond,    -   e. it being possible for two vicinal Z¹ to Z⁶ groups together to        form an electron-withdrawing or non-electron-withdrawing ring        which is advantageously other than the carbene L_(γ) of        formula (II) and which optionally comprises heteroatoms        (preferably O, N or S);        -   or together form the ligand L_(δ) of formula (IV):        -   in which:        -   Y₁ and Y₂ represent, independently of one another,            CR_(a)R_(b) or SiR_(c)R_(d);        -   X represents O, NR_(e) or CR_(f)R_(g);        -   R¹⁰, R¹¹, R¹³ and R¹⁴, which are identical or different, are            chosen from a hydrogen atom, an alkyl group or an aryl group            optionally substituted by alkyl;        -   R⁹, R¹², R_(a), R_(b), R_(c) and R_(d) are chosen            independently from a hydrogen atom; an alkyl group; an acyl            group; an aryl group optionally substituted by alkyl; a            cycloalkyl group optionally substituted by alkyl; and an            arylalkyl group in which the aryl part is optionally            substituted by alkyl;        -   R_(c) and R_(d) are chosen independently from alkyl; aryl            optionally substituted by alkyl; cycloalkyl optionally            substituted by alkyl; and arylalkyl in which the aryl part            is optionally substituted by alkyl; or else        -   when Y₁ and Y₂ independently represent SiR_(c)R_(d), two            R_(c) groups bonded to two separate silicon atoms together            form a chain of formula:            -   in which n is an integer from 1 to 3; X is as defined                above; R and R′, which are identical or different, take                any one of the meanings given above for R_(e), it being                understood that, when n is 2 or 3, only one silicon atom                of the said chain may be substituted by one or two                alkenyl or alkynyl groups; or else            -   when Y₁ and Y₂ independently represent SiR_(c)R_(d), two                R_(c) groups bonded to separate silicon atoms together                form a saturated hydrocarbonaceous chain, the two R_(c)                groups forming, together with the said silicon atoms and                X, a 6- to 10-membered ring; or else            -   when Y₁ and Y₂ independently represent CR_(a)R_(b), two                R_(a) groups bonded to separate carbon atoms together                form a saturated hydrocarbonaceous chain, the two R_(a)                groups forming, together with the carbon atoms which                carry them and X, a 6- to 10-membered ring; and            -   R_(f) and R_(g) represent, independently of one another,                a hydrogen atom; an alkyl group; an acyl group; an aryl                group optionally substituted by alkyl; a cycloalkyl                group optionally substituted by alkyl; an arylalkyl                group in which the aryl part is optionally substituted                by alkyl; a halogen atom; an alkenyl group; an alkynyl                group; or an SiG₁G₂G₃ group where G₁, G₂ and G₃ are,                independently of one another, alkyl; alkoxy; aryl                optionally substituted by alkyl or alkoxy; or arylalkyl                in which the aryl part is optionally substituted by                alkyl or alkoxy.

The presence of specific metal/heterocyclic carbene complexes in thecompositions according to the invention confers great stability on thelatter in an ambient atmosphere under standard temperature, humidity andpressure conditions. Such silicone compositions can be stored in thesingle-component form, in the uncrosslinked state, in an ambientatmosphere, for long periods of time (for example, from 1 to severalmonths). This result is all the more advantageous and surprising since,with some metal/heterocyclic carbene catalysts, it is possible todispense with the use of crosslinking inhibitors or, at the very least,to use less thereof, which is entirely beneficial economically and withregard to limiting the negative repercussions on the crosslinking of theelastomer and its final qualities.

This stability goes together with the ability which the compositionsaccording to the invention have to crosslink under hot conditions (forexample from 100° C.) by hydrosilylation into elastomers of goodquality, in particular at the structural and mechanical level. Inaddition, the kinetics of the reaction are satisfactory.

These single-component silicone compositions, which have a long pot lifeat ambient temperature, are all the more advantageous because their costis not prohibitive. This advantage is even more marked when they do notcomprise an inhibitor.

The definition of the metal complexes of formula (I) constituting thecatalyst —C—, an essential compound of the composition according to theinvention, is completed below.

The metals of Group 8 represented by M in the formula (I) are, forexample, palladium, platinum or nickel in the zero oxidation state. Inpractice, M represents platinum in the 0 oxidation state.

The term “alkyl” denotes a saturated, linear or branched,hydrocarbonaceous chain which is optionally substituted (e.g. by one ormore alkyls), preferably with from 1 to 10 carbon atoms.

Examples of alkyl groups are in particular methyl, ethyl, isopropyl,n-propyl, tert-butyl, n-butyl or n-pentyl.

The alkyl part of the alkoxy radical is as defined above.

The term “cycloalkyl” is understood to mean a saturated, mono- orpolycyclic, preferably mono- or bicyclic, hydrocarbonaceous radicalpreferably exhibiting from 3 to 10 carbon atoms.

The term “saturated polycyclic hydrocarbonaceous radical” is understoodto mean a radical exhibiting two or more rings attached to one anothervia σ bonds and/or condensed in pairs.

Examples of polycyclic cycloalkyl groups are adamantyl and norbornyl.

Examples of monocyclic cycloalkyl groups are cyclopentyl and cyclohexyl.

The term “perfluorinated alkyl” denotes an alkyl comprising at least oneperfluoroalkyl group preferably having the formula:—(CH₂)_(p)—C_(q)F_(2q+1)in which p represents 0, 1, 2, 3 or 4; q is an integer from 1 to 10; andC_(q)F_(2q+1) is linear or branched.

The expression “aryl” denotes a monocyclic or polycyclic, preferablymonocyclic or bicyclic, aromatic hydrocarbonaceous group having from 6to 18 carbon atoms. It should be understood that, in the context of theinvention, the term “polycyclic aromatic radical” is understood todenote a radical exhibiting two or more aromatic nuclei condensed(ortho-condensed or ortho- and peri-condensed) with one another.

The said aromatic hydrocarbonaceous (“aryl”) group is optionallysubstituted, for example by one or more C₁-C₃ alkyls, one or morehalogenated hydrocarbonaceous radicals (e.g. CF₃), one or more alkoxys(e.g. CH₃O) or one or more hydrocarbonaceous radicals comprising one ormore ketone units (e.g. CH₃CO—).

Mention may be made, as examples of aryl, of the phenyl and naphthylradicals.

The expression “arylalkyl” denotes an alkyl group as defined abovesubstituted on its hydrocarbonaceous chain by one or more aryl groups,the aryl group being as defined above. Examples thereof are benzyl andtriphenylmethyl.

The term “acyl” is understood to denote an R^(o)—CO— group where R^(o)represents an alkyl as defined above; or else an Ar—CO— group where Arrepresents an aryl group as defined above; or else an arylalkyl in which“aryl” and “alkyl” are as defined above and in which the aryl part isoptionally substituted, e.g. by an alkyl.

The term “alkenyl” is understood to denote an unsaturated, substitutedor unsubstituted, linear or branched, hydrocarbonaceous chain exhibitingat least one olefinic double bond and more preferably a single doublebond. Preferably, the alkenyl group exhibits from 2 to 8 carbon atoms,better still from 2 to 6. This hydrocarbonaceous chain optionallycomprises at least one heteroatom, such as O, N or S. Preferred examplesof alkenyl groups are the allyl and homoallyl groups.

The term “alkynyl” is understood to denote, according to the invention,an unsaturated, substituted or unsubstituted, linear or branched,hydrocarbonaceous chain exhibiting at least one acetylenic triple bondand more preferably a single triple bond. Preferably, the alkynyl groupexhibits from 2 to 8 carbon atoms, better still from 2 to 6 carbonatoms. Mention may be made, by way of examples, of the acetylenyl groupand the propargyl group. This hydrocarbonaceous chain optionallycomprises at least one heteroatom, such as O, N or S.

The expression “does not represent anything” means that the -T₃ and -T₄substituents respectively do not exist. This is because, in the formula(II), the nitrogen atom is trivalent, so that, when A or B represents N,the nitrogen atom cannot have an additional substituent.

Preferably, in the carbene ligands of formula (II):

(i) T₃ and T₄ represent a hydrogen atom or together form a phenyl,

and/or

(ii) T₁ and T₂, which are identical or different, represent(s) amonovalent radical of following formula (V):*Z₁-Z₂   (V)

in which:

-   -   Z₁ is a divalent hydrocarbonaceous radical, preferably an        alkylene,    -   Z₂ is a monovalent radical chosen from:        -   a (C₅-C₃₀)cycloalkyl radical comprising at least one            heteroatom in the ring, preferably nitrogen,        -   a (C₆-C₃₀)aryl radical comprising at least one heteroatom in            the aromatic ring, preferably nitrogen,

and/or

(iii) A and B both represent a carbon atom.

The ligands L_(α) and L_(β) of the catalyst —C— of formula (I) belongingto the composition according to the invention can independentlyrepresent an alkyne of formula (III.1) or an alkene of formula (III.2)substituted by Z¹ to Z⁶ radicals carrying at least oneelectron-withdrawing unit active with respect to π unsaturation of L_(α)and L_(β), in order to promote the liganding with the metal M of thecomplex.

Advantageously, in the formulae (III.1) and (III.2), theelectron-withdrawing residues are chosen from the group consisting of:

in which:

R₁₇, R₁₈, R₁₉ and R₂₀, which are identical or different, are substitutedor unsubstituted alkyl, alkenyl or alkynyl and n′ is between 1 and 50.

Mention may be made, by way of examples of Z¹ to Z⁶ radicals, of:

-   -   those selected from the group consisting of:        —CN, —COOCH₃, —COOCH₂CH₃, —CONC₁₂H₂₅    -   and, in the cases where the Z¹ and Z² substituents form in pairs        and with the triple bond, in (III.1), a ring Cy1 and where Z³ to        Z⁶ form in pairs, with or without the double bond, in (III.2), a        ring Cy2, these rings Cy1 and Cy2 are independently and        preferably chosen from the group consisting of the following        rings:

When L_(α) and L_(β) together form a ligand L_(δ) of formula (IV), thelatter is preferably of the type of those in which Y₁ and Y₂ either bothrepresent CR_(a)R_(b) or both represent SiR_(c)R_(d), so that the saidcomplexes either have the formula (IV.1) or have the formula (IV.2):

where:the two R_(a) groups, the two R_(b) groups, the two R_(c) groups and thetwo R_(d) groups are identical to one another and R⁹═R¹²; R¹⁰═R¹⁴; andR¹¹═R¹³. Preferably, X═O.

According to an alternative form, the two R_(c) groups in (IV.2)together form (a) either a chain

in which n is an integer from 1 to 3; X is as defined above; and R andR′, which are identical or different, take any one of the meanings givenabove for R_(d), it being understood that, when n is 2 or 3, only onesilicon atom of the said chain may be substituted by one or two alkenylor alkynyl groups;

(b) or a saturated hydrocarbonaceous chain, so that the two R_(c)substituents form, together with the two silicon atoms which carry themX, a 6- to 10-membered ring, preferably a 6- to 8-membered ring.

In this respect, more detailed and preferred examples of structuresR_(c)-R_(c) are given in Application WO 01/42258, page 7, line 11 topage 9, line 19, under the form “Rd¹-Rd²”.

In the context of the invention, the expression “independentlyrepresent” means that the designated substituents are either identicalor different.

Preferred meanings of R₉ and R₁₂ are in particular a hydrogen atom; analkyl group; an aryl group optionally substituted by alkyl; and acycloalkyl group optionally substituted by alkyl.

For example, the diolefinic ligand L_(δ) of formula (IV) is symmetrical,that is to say that R₁₀═R₁₄; R₁₁═R₁₃; R₉═R₁₂ and the two groups Y₁ andY₂ are either strictly identical to one another, or Y₁═CR_(a)R_(b) andY₂═CR_(a)R_(b), or Y₁═SiR_(c)R_(d) and Y₂═SiR_(c)R_(d).

As regards the catalyst —C— of the composition according to theinvention, mention should be made of a first particularly preferredgroup of metal complexes of following formula (I.1):

in which:

-   -   T₁ and T₂ are identical and are as defined above;    -   T₃ and T₄ are as defined above;    -   R_(c) and R_(d) are as defined above.

A second particularly preferred group of catalysts —C— of thecomposition according to the invention comprises the metal complexes offollowing formula (I.2):

in which:

-   -   T₁ and T₂ are identical and are as defined above;    -   T₃ and T⁴ are as defined above;    -   Z₃ to Z₆ are as defined above.

A third particularly preferred group of catalysts —C— of the compositionaccording to the invention comprises the metal complexes of followingformula (I.3):

in which:

-   -   T₁ and T₂ are identical and are as defined above;    -   T₃ and T₄ are as defined above;    -   and Z₁ and Z₂ are as defined above.

In addition to the catalyst —C—, the composition according to theinvention comprises the two polyorganosiloxane entities reactive bypolyaddition, namely the POS -A- and the POS —B—. The latter are chosenfrom the POSs composed of siloxyl units of general formula:(R²⁰)_(x)SiO_((4-x)/2)   (I′)and/or of siloxyl units of formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′)in which formulae the various symbols have the following meanings:

-   -   the R²⁰ and R²² symbols, which are identical or different, each        represent a group with a nonhydrolysable hydrocarbonaceous        nature, it being possible for this radical to be:        -   an alkyl or haloalkyl radical having from 1 to 5 carbon            atoms and comprising from 1 to 6 chlorine and/or fluorine            atoms,        -   cycloalkyl and halocycloalkyl radicals having from 3 to 8            carbon atoms and comprising from 1 to 4 chlorine and/or            fluorine atoms,        -   aryl, alkylaryl and haloaryl radicals having from 6 to 8            carbon atoms and comprising from 1 to 4 chlorine and/or            fluorine atoms,        -   cyanoalkyl radicals having from 3 to 4 carbon atoms;    -   the R²¹ symbols, which are identical or different, each        represent a hydrogen atom, a C₂-C₆ alkenyl group, a hydroxyl        group, a hydrolysable atom or a hydrolysable group;    -   x=an integer equal to 0, 1, 2, or 3;    -   y=an integer equal to 0, 1, 2, or 3;    -   z=an integer equal to 0, 1 or 2;    -   the sum y+z is between 1 and 3;    -   with the condition according to which the Si-alkenyl POS -A-        comprises at least one unit R²¹=alkenyl per molecule and the        Si—H POS —B— comprises at least one unit R²¹=hydrogen per        molecule.

These POSs -A- and —B— are, for example, respectively apolyorganovinylsiloxane and a polyorganohydrosiloxane. The organicsubstituents, other than the vinyl reactive groups and the hydrogen,are, for example, methyls or phenyls. The hydrogens and the vinyls arecarried by siloxyl units M=[R₃SiO—] and/or D=[-(R)₂SiO—] and/orT=[-(R)SiO—]. These hydrogenated or vinylated units M and D eachcomprise one or more H or vinyl units, preferably only one.

The number of SiH or SiVi units per molecule is at least equal to 2 andpreferably at greater than 2.

This can represent from 0.01% to 10% (preferably 0.1 to 2%) of vinylgroup (27 g/mol) by weight for the POS -A- and from 0.001% to 5%(preferably 0.05 to 2%) of hydrogen group (lg/mol) by weight for the POS—B—.

Generally, the POSs -A- and —B— which can be used in the reaction havean average molecular mass of between 1×10² and 1×10⁷ (g/mol).

For the POS -A-, this encompasses in particular, in terms of dynamicviscosity at 25° C., ranges:

-   -   of POSs which can be cured under hot conditions (HCE) by        polyaddition, having a viscosity at least equal to 1×10⁵ mPa·s,        preferably of between 1×10⁶ and 1×10⁷ mPa·s,    -   and of POSs which can be cured under hot conditions by        polyaddition, of liquid silicone elastomer (LSR) type, having a        viscosity preferably of between 1×10⁵ and 5×10⁵ mPa·s.

According to a preferred form of the invention, the siliconecompositions concerned are POSs which can be cured under hot conditions(HCE) by polyaddition and in which the POSs -A- can have in practice aviscosity at 25° C. of, e.g., 2×10⁶ mPa·s and the POSs —B— of 10 to 5000 mPa·s (e.g. 300 mPa·s).

In these examples, the viscosity is measured using a Brookfieldviscometer according to the directions of the AFNOR Standard NFT 76 106of May 82.

All the viscosities concerned in the present account correspond to a“Newtonian” dynamic viscosity quantity at 25° C., that is to say thedynamic viscosity which is measured, in a way known per se, at a shearrate gradient which is sufficiently low for the viscosity measured to beindependent of the rate gradient.

The composition according to the invention can also comprise a certainnumber of conventional ingredients in addition to the POSs -A- and —B—and the catalyst —C—, including in particular at least one crosslinkinginhibitor -D- capable of slowing down the polyaddition reaction and ofmaking possible the storage of the single-component composition-A-B-C-D- in a not entirely crosslinked state.

The invention consequently relates to silicone compositions comprisingat least one inhibitor -D- and in which the catalyst —C— is chosen frommetal complexes of formula (I.1), formula (I.2), where Z3 to Z6 aredevoid of electron-withdrawing residue(s), and formula (I.3), where Z1and Z2 are devoid of electron-withdrawing residue(s). These compositionshave long storage times (pot lives).

It should be noted that for some catalysts —C—, in particular thosecomprising a carbene (II) and at least one (preferably two) ligandsL_(α) and L_(β) of formula (III.1) or (III.2), it is not necessary touse an inhibitor.

The invention is consequently also targeted at silicone compositionsdevoid of inhibitor -D- and in which the catalyst —C— is chosen frommetal complexes:

-   -   of formula (I.2), where T₁, T₂, T₃, T₄, R_(c) and R_(d) are as        defined above and at least one of the Z³ to Z⁶ substituents        (preferably each substituent) comprises at least one        electron-withdrawing residue;    -   and/or of formula (I.3), where T₁, T₂, T₃ and T₄ are as defined        above and Z¹ and Z² are devoid of electron-withdrawing        residue(s).

These inhibitor-free compositions have, entirely advantageously andunexpectedly, long storage lives (pot lives) in an ambient atmosphere.Cross-linking only occurs under hot conditions. This advantage is amajor one economically and with regard to convenience of use and ofstorage.

Advantageously, the inhibitors -D- (if they are employed) are selectedfrom:

-   -   polyorganosiloxanes, advantageously cyclic polyorganosiloxanes,        substituted by at least one alkenyl,        tetramethylvinyl-tetrasiloxane being particularly preferred,    -   alkyl, alkenyl or alkynyl maleates, diallyl maleate being        particularly preferred,    -   acetylenic alcohols,    -   and/or alkyl, alkenyl or alkynyl acetylenedicarboxylates.

Such an inhibitor -D- is present in a proportion of at most 3 000 ppm,preferably in a proportion of 100 to 2 000 ppm, with respect to thetotal weight of the polyorganosiloxanes -A- and —B—.

Mention may be made, as conventional families of conventional functionaladditives capable of being employed in the silicone compositionsaccording to the invention, of:

-   -   fillers,    -   hydroxylated POS oils of use as compatibilizer,    -   adhesion promoters,    -   adhesion modifiers,    -   pigments,    -   additives for stability towards heat, oils or fire (for example,        metal oxides).

The fillers optionally provided are preferably inorganic fillers. Theycan be composed of products chosen from siliceous materials which canact as reinforcing or semi-reinforcing filler.

Reinforcing siliceous fillers are chosen from colloidal silicas, fumedand precipitated silica powders, or their mixture.

Semi-reinforcing siliceous fillers, such as diatomaceous earths orground quartz, can also be employed.

As regards nonsiliceous inorganic materials, they can be used assemi-reinforcing or bulking inorganic filler.

Examples of these nonsiliceous fillers, which can be used alone or as amixture, are carbon black, titanium dioxide, aluminium oxide, aluminahydrate, expanded vermiculite, nonexpanded vermiculite, calciumcarbonate, zinc oxide, mica, talc, iron oxide, barium sulphate andslaked lime.

Conveniently but without implied limitation, the fillers employed can bea mixture of quartz and silica.

The fillers can be treated with any appropriate product.

It is preferable, by weight, to employ an amount of filler of between 20and 50, preferably between 25 and 35% by weight, with respect to thecombined constituents of the composition.

More generally, the amounts in the compositions according to theinvention are standard proportions in the technical field underconsideration, it being understood that the targeted application alsohas to be taken into account.

According to another of its aspects, the present invention relates, asnovel products, to the complexes of formula (I) as defined above, of usein particular as catalysts —C—.

The invention additionally relates to any catalytic compositioncomprising, as active material, one or more metal complexes of formula(I) as defined above.

Such catalysts (in particular hydrosilylation catalysts) have thedistinctive characteristic that they can be formed in situ in siliconecompositions of the type of those according to the invention, providedthat the compositions comprise ligands L_(α) and L_(β) of formula(III.1) or (III.2), for example as inhibitor -D-. This or these ligandsL_(α) and L_(β) of formula (III.1) or (III.2) are capable of displacingthe initial ligands L_(δ) from the catalyst —C—. These are latentcatalysts. The present invention obviously encompasses this scenario.

Another subject-matter of the invention is a process for thehydrosilylation of olefins or of acetylenic derivatives (for example,hydrosilylation of one or more POSs -A- using one or more POSs —B—),characterized in that it consists in employing the silicone compositionas defined above and/or the catalytic composition also described above.

According to an advantageous alternative form in which recourse is hadto at least one latent catalyst as described above, use is made of asilicone composition according to the invention as presented abovecomprising at least one inhibitor -D- which makes possible the in situformation of at least one metal complex comprising at least one ligandL_(α) or L_(β) of formula (III.1) or (III.2).

The hydrosilylation reaction can be carried out in a solvent or in theabsence of solvent. In an alternative form, one of the reactants can actas solvent: for example, the compound comprising an ethylenic doublebond or comprising an acetylenic triple bond.

Appropriate solvents are solvents which are miscible with the compoundcomprising an Si—H unit.

Under the conditions of the hydrosilylation reaction, the catalystcomplex must be dissolved in the reaction medium.

Examples of solvents which can be used for the hydrosilylation are inparticular aliphatic hydrocarbons, aromatic hydrocarbons, halogenatedaliphatic or aromatic hydrocarbons, or ethers.

The hydrosilylation reaction can be carried out at a temperature ofbetween 15° C. and 300° C., for example between 20 and 240° C.

Generally, the molar ratio of the unsaturations to the Si—H bonds variesbetween 1:100 and 10:1.

According to the invention, the hydrosilylation reaction is carried outin the presence of a catalytic amount of one or more complexes offormula (I). The term “catalytic amount” is understood to denote lessthan one molar equivalent of a metal choosen from the metals of group 8with respect to the amount of unsaturations present in the reactionmedium.

Generally, it is sufficient to introduce, into the reaction medium, lessthan 1 000 ppm, preferably less than 100 ppm, better still less than 50ppm, of the metal of group 8, calculated with respect to the total massof the unsaturated compound and of the compound comprising Si—H units.

As regards the preparation of the composition according to theinvention, it relates to employing and mixing the compounds -A-, —B—,—C—, optionally -D- and one or more other conventional additives.

The mixing operations are entirely within the scope of a person skilledin the art.

The POSs -A- and —B—, the inhibitors -D- and the other conventionaladditives, such as fillers, are commodities fully available/accessibleto a person skilled in the art.

As regards the metal complexes (I) forming the catalysts —C—, it hasbeen seen above that the catalysts —C— comprising complexes:

with L_(α) and/or L_(β) of formula (III.1) or (III.2), can be obtainedfrom complexes (I) in which L_(γ) is of formula (II) and L_(α) and L_(β)are of formula (IV), the latter being displaced in situ by inhibitors-D- of formula (III.1) or (III.2).

These complexes (I) in which L_(γ) is of formula (II) and L_(α) andL_(β) are of formula (IV) are prepared conventionally, for example fromknown complexes of the state of the art, by ligand exchange, that it tosay by addition of the appropriate carbene of formula (II) to a metalcomplex of the metal M in solution, denoted precursor complex.

Appropriate precursor complexes are, for example, the Karstedt complex.

The complexes of formula (I) are generally prepared from precursorcomplexes exhibiting, as ligand, at least one diolefinic compound offormula (IV.P):

in which R₁, R₂, R₃, R₄, R₅, R₆, X, Y₁ and Y₂ are as defined above forthe formula (I).

These ligands are either commercially available or are easily preparedby a person skilled in the art from commercial compounds. In thisrespect, reference may be made to the information given in ApplicationWO 01/42258, more particularly page 15, line 1 to page 18, line 14.

The carbenes of formula (II) can be prepared by deprotonation ofimidazolium salts, of tetrazolium salts, of triazolium salts or ofpyrazolium salts, according to the situation, under the action of abase.

These reactions can be represented schematically as follows:

In these reaction schemes, T₁, T₂, T₃, T₄, A and B are as defined abovefor the formula (I) and X⁻ represents an anion.

The nature of the anion X⁻ is not critical according to the invention.The anion X⁻ is the anion derived from an organic or inorganic Brönstedacid (protic acid) . The anion X⁻ is usually derived from an acidexhibiting a pK_(a) of less than 6. Preferably, X⁻ derives from an acidwith a pK_(a) of less than 4, better still of less than 2. The pK_(a)values concerned with here are the pK_(a) values of the acids asmeasured in water.

Examples of acids are sulphonic acids and phosphonic acids.

Mention will be made, as sulphonic acid, of benzenesulphonic acid andmention will be made, as phosphonic acid, of phenylphosphonic acid.

According to the invention, the anions X⁻ derived from the acids HCl,HBr, H₂SO₄, HBF₄ and H₃PO₄ are more particularly preferred.

The bases which can be used for the deprotonation of the salts offormula (VIII.1) are strong bases chosen from alkali metal hydrides,alkali metal carboxylates, alkali metal alkoxides and alkali metalamides.

Examples of appropriate bases are therefore sodium hydride, sodiummethoxide, potassium tert-butoxide, lithium diisopropylamide and theirmixtures.

The deprotonation reaction is preferably carried out in a solventcapable of at least partially dissolving the starting salt of formula(VIII.1) and the other reactants.

The nature of the solvent also depends on the strength of the base. Thisis because, in the case of a strong base and of particularly reactivestarting salts, it may be necessary to operate at a low temperature.

Generally, the reaction temperature is between −78° C. and 40° C.,preferably between −50 and 30° C., better still between −40 and 25° C.,for example between −30 and 20° C.

Solvents which can be used in the process for the preparation of thecarbenes are cyclic or noncyclic ethers.

Other preparation methods suitable for the synthesis of the carbenes offormula (II) are shown in Application WO 01/42258.

According to a particularly preferred embodiment of the invention, themetal complex of the invention has the formula:

in which L_(γ) is as defined above.

A simple method for the preparation of this complex consists in reactingthe carbene L with the “conventional” Karstedt catalyst. This reactioncan be carried out in bulk or in a solvent.

Examples of appropriate solvents are cyclic or noncyclic ethers, amidesand aromatic hydrocarbons. The reaction temperature usually variesbetween 10 and 50° C. It is desirable to carry out the reaction in thepresence of a slight excess of carbene with respect to the platinum.

Another advantageous preparation process consists in bringing together:

-   -   at least one salt of formula (VIII):        -   in which:        -   A, B, T₁, T₂, T₃ and T₄ are as defined above;        -   Z₇ independently represents an anion derived from a Brönsted            acid (protic acid),    -   at least one appropriate precursor complex of formula (IV.P),    -   at least one solvent (selected in particular from those        mentioned above),    -   and at least one base (selected in particular from those        mentioned above).        In this respect, a detailed description of the latter process is        shown in French Application No. 01/07473, filed on 7 Jun. 2001.

The catalysts thus prepared can be used in hydrosilylation reactions.They make possible homogeneous catalysis of the reaction.

They also give access to single-component silicone compositions,preferably of polyaddition HCE type, exhibiting much longer pot livesthan those prepared with conventional platinum-based catalysts, whileusing only very little or nothing in the way of inhibitors -D-.

The invention is illustrated in the light of the following examples.

EXAMPLES

The Pt-Carbene complexes used in the examples have the structuresdescribed below:

1. Synthesis of the Complex 2

The complex 2 was prepared according to the process disclosed in thedocument WO 01/42558.

2. Synthesis of the Complex 1

1,3-Bis(2-pyridyl)imidazolium chloride, used for the preparation of thecomplex 1, is synthesized according to the procedure described in thejournal Organometallics, 2000, 19, 5113.

0.78 g of 1,3-bis(2-pyridyl)imidazolium chloride (3 mmol) and then 4.66g of a Karstedt catalyst solution comprising 11.3% of Pt by weight (2.7mmol of Pt) are introduced into a 250 ml reactor dried beforehand in anoven. 100 ml of anhydrous THF are subsequently added. 3.0 ml of 1Msolution of t-BuOK in THF (3 mmol) are then injected over 30 min at 0°C.

The reaction mixture is stirred for an additional hour and then filteredand purified (conventional purification method).

3. Preparation of Crosslinkable Silicone Elastomer Composition

Each composition was prepared according to the following procedure:

An amount of catalyst equivalent to 67 ppm of Pt (calculated withrespect to the total mass of vinylsiloxane oil and of hydrosiloxane oil)is dissolved in a few μl of toluene. 10 parts of an α,ω-vinylsiloxaneoil, with a viscosity equal to 230 mPa·s and comprising 0.61% by mass ofvinyl groups, are added to the solution. In example 3.1 no additionalinhibitor is added. In example 3.2 a quantity of inhibitor(3,7,11-trimethyldodecyn-1-ol=TMDDO) is then added, if appropriate(Example 3.2), to produce the desired inhibitor/Pt molar ratio.

After rapid stirring, 2.7 parts of a hydrosiloxane oil, with a viscosityequal to 300 mPa·s and comprising 0.17% by mass of hydrogen, are added.

The DSC analyses of the preceding formulations are described below:Temp. Peak of Begin- Temp. the Gelling Cata- Inhib- ning End exothermtime at lyst itor/Pt (° C.) (° C.) (° C.) 25° C. Example 3.1 1 / 106 122114  30 days 3.2 1 60 150 163 154 >15 weeks Counter- example 1 2 / 95123 107  1 day 2 2 60 152 177 164  13 weeks

The DSC curves and the gelling time at 25° C. show that the claimedcomplexes exhibit a satisfactory activity and result in more stablesilicone compositions which can be crosslinked into elastomers.

1.-12. (canceled)
 13. A silicone composition which is crosslinkable byhydrosilylation, said composition comprising at least onePolyOrganoSiloxane -A- (POS) carrying ethylenic and/or acetylenicunsaturation(s), at least one polyorganohydrosiloxane —B—, a metalcatalyst —C— and optionally at least one inhibitor -D- of thehydrosilylation reaction; said catalyst —C— comprising at least onecompound having the formula (I):

in which: M represents a metal of Group 8 of the Periodic Table; L_(γ)represents a carbene of formula (II):

in which: A and B, which are identical or different, represent C or N,it being understood that, when A represents N, then T₄ does notrepresent anything and, when B represents N, then T₃ does not representanything; T₃ and T₄ independently represent a hydrogen atom; an alkylgroup; a cycloalkyl group optionally substituted by alkyl or alkoxy; anaryl group optionally substituted by alkyl or alkoxy; an alkenyl group;an alkynyl group; or an arylalkyl group in which the aryl part isoptionally substituted by alkyl or alkoxy; or T₃ and T₄ can together andwith A and B, when the latter each represent a carbon atom, form anaryl; T₁ and T₂ independently represent an alkyl group; an alkyl groupoptionally substituted by alkyl; a perfluorinated alkyl group or analkyl group optionally substituted by a perfluoroalkyl group; acycloalkyl group optionally substituted by alkyl or alkoxy; an arylgroup optionally substituted by alkyl or alkoxy; an alkenyl group; analkynyl group; or an arylalkyl group in which the aryl part isoptionally substituted by alkyl or alkoxy; or T₁ and T₂ independentlyrepresent a monovalent radical of following formula (V):V₁-V₂   (V) in which: V₁ is a divalent hydrocarbonaceous radical, V₂ isa monovalent radical selected from the group consisting of the followingsubstituents: alkoxy, —OR^(o) wherein R^(o) is hydrogen, alkyl or aryl,and amine; T₁ and T₂ independently represent a monovalent radical offollowing formula (W):W₁-ω-W₂   (W) in which: W₁ is a divalent hydrocarbonaceous radical; ωrepresents: —R¹C═CR¹— wherein R¹ is H or alkyl, or—C≡C—; W₂ is a monovalent radical selected from the group consisting ofthe following substituents: R², which is alkyl or H; Si-alkyl orSi-alkoxy; alcohol; ketone; carboxyl; amide; and acyl; or thesubstituents T₂, T₂, T₃ and T₄ form in pairs, when they are situated attwo adjacent points in the formula (II), a saturated or unsaturatedhydrocarbonaceous chain; and with the condition that at least onesubstituent T₁ and/or T₂, which are identical or different, represent(s)a monovalent radical of following formula (V):Z₁-Z₂   (V) in which: Z₁ is a divalent hydrocarbonaceous radical, and Z₂is a monovalent radical selected from the group consisting of: a(C₅-C₃₀)cycloalkyl radical having at least one heteroatom in the ring,and a (C₆-C₃₀)aryl radical having at least one heteroatom in thearomatic ring, L_(α) and L_(β) are ligands which are identical to ordifferent from each other and each represent:

wherein, in these formulae (111.1) and (111.2): Z¹, Z², Z³, Z⁴, Z⁵ andZ⁶ each independently represent: hydrogen, halogen, cyano, or asaturated or unsaturated, electron-withdrawing ornon-electron-withdrawing, hydrocarbonaceous group, or two vicinal Z¹ toZ⁶ groups together form an electron-withdrawing ornon-electron-withdrawing ring which optionally comprises heteroatoms; orL_(α) and L_(β) together form the ligand L_(δ) of formula (IV):

in which: Y₁ and Y₂ represent, independently of each other, CR_(a)R_(b)or SiR_(c)R_(d); X represents O, NR_(e) or CR_(f)R_(g); R¹⁰, R¹¹, R¹³and R¹⁴, which are identical or different, are selected from the groupconsisting of a hydrogen atom, an alkyl group and an aryl groupoptionally substituted by alkyl; R⁹, R¹², R_(a), R_(b) and R_(e) areselected independently from the group consisting of a hydrogen atom; analkyl group; an acyl group; an aryl group optionally substituted byalkyl; a cycloalkyl group optionally substituted by alkyl; and anarylalkyl group in which the aryl part is optionally substituted byalkyl; R_(c) and R_(d) are selected independently from the groupconsisting of alkyl; aryl optionally substituted by alkyl; cycloalkyloptionally substituted by alkyl; and arylalkyl in which the aryl part isoptionally substituted by alkyl; or when Y₁ and Y₂ independentlyrepresent SiR_(c)R_(d), two R_(c) groups bonded to two separate siliconatoms together form a chain of the formula:

in which n is an integer from 1 to 3; X is as defined above; R and R′,which are identical or different, have any one of the meanings givenabove for R_(e), it being understood that, when n is 2 or 3, only onesilicon atom of the said chain may be substituted by one or two alkenylor alkynyl groups; or when Y₁ and Y₂ independently representSiR_(c)R_(d), two R_(c) groups bonded to separate silicon atoms togetherform a saturated hydrocarbonaceous chain, the two R_(c) groups forming,together with the said silicon atoms and X, a 6- to 10-membered ring; orwhen Y₁ and Y₂ independently represent CR_(a)R_(b), two R_(a) groupsbonded to separate carbon atoms together form a saturatedhydrocarbonaceous chain, the two R_(a) groups forming, together with thecarbon atoms which carry them and X, a 6- to 10-membered ring; and R_(f)and R_(g) represent, independently of each other, a hydrogen atom; analkyl group; an acyl group; an aryl group optionally substituted byalkyl; a cycloalkyl group optionally substituted by alkyl; an arylalkylgroup in which the aryl part is optionally substituted by alkyl; ahalogen atom; an alkenyl group; an alkynyl group; or an SiG₁G₂G₃ groupwhere G₁, G₂ and G₃ are, independently of one another, alkyl; alkoxy;aryl optionally substituted by alkyl or alkoxy; or arylalkyl in whichthe aryl part is optionally substituted by alkyl or alkoxy.
 14. Acomposition according to claim 13, wherein M is Pt, Pd or Ni in the zerooxidation state.
 15. A composition according to claim 13, wherein in theformula (II): T₃ and T₄ represent a hydrogen atom or together formphenyl, and/or T₁ or T₂ represents (C₁-C₈)alkyl or (C₃-C₈)cycloalkyl,and/or A and B both represent a carbon atom.
 16. A composition accordingto claim 13, wherein in formulae (III.1) and (III.2), theelectron-withdrawing groups are selected from the group consisting of:

in which: R₁₇, R₁₈, R₁₉ and R₂₀ are each a substituted or unsubstitutedalkyl, alkenyl or alkynyl and n′ is between 1 and
 50. 17. A compositionaccording to claim 13, wherein: Z¹, Z², Z³, Z⁴, Z⁵ and Z⁶ are selectedfrom the group consisting of —COOCH₃, —COOCH₂CH₃, —CONC₁₂H₂₅ and —CN;or, wherein, when the Z¹ and Z² substituents form in pairs and with thetriple bond, in (III.1), a ring Cy1 or wherein when Z³ to Z⁶ form inpairs, with or without the double bond, in (III.2), a ring Cy2, saidrings Cy1 and Cy2 are independently selected from the group consistingof:


18. A composition according to claim 13, wherein L_(α) and L_(β)together form a ligand L_(δ) of formula (IV) in which Y₁ and Y₂ eitherboth represent CR_(a)R_(b) or both represent SiR_(c)R_(d), so that thecomplexes have the formula (IV.1) or the formula (IV.2):

wherein the two R_(a) groups, the two R_(b) groups, the two R_(c) groupsand the two R_(d) groups are identical to one another and R⁹═R¹²;R¹⁰═R¹⁴; and R¹¹═R¹³.
 19. A composition according claim 13, wherein thecatalyst —C— has the formula (I.1):

in which: T₁ and T₂ are identical and are as defined in claim 13; T₃ andT₄ are as defined in claim 13; and and R_(c) and R_(d) are as defined inclaim
 13. 20. A composition according to claim 13, wherein the POSs -A-and —B— are chosen from those composed of siloxyl units of the formula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 21. The composition according to claim 13, wherein V₁ isalkylene and, when V₂ is an amine, it has the formula N(R^(o))₂ whereinR^(o) is hydrogen, alkyl or aryl.
 22. The composition according to claim13, wherein W₁ is linear or branched C₁-C₁₀ alkylene, which isoptionally substituted.
 23. The composition according to claim 13,wherein W₂ is alkyl, H, —Si(R³)₃ wherein R³ is alkyl, C(R⁴)₂OH whereinR⁴ is H or alkyl, —C(O)R⁵ wherein R⁵ is alkyl, —C(O)OR⁶ wherein R⁶ isalkyl, —C(O)N(R⁷)₂ wherein R⁷ is H or alkyl, or —OC(O)R⁸ wherein R⁸ isalkyl.
 24. The composition according to claim 13, wherein in formula(V), Z₁ is alkylene and Z₂ is (C₅-C₃₀)cycloalkyl having at least onenitrogen atom in the ring or (C₆-C₃₀)aryl having at least one nitrogenatom in the aromatic ring.
 25. The composition according to claim 13,wherein in formula (III.1) and (III.2), when Z¹, Z², Z³, Z⁴, Z⁵ and/orZ⁶ is an unsaturated electron-withdrawing or non-electron-withdrawing,hydrocarbonaceous group, it is unsaturated adjacent to the double ortriple bond.
 26. The composition according to claim 13, wherein informulae (III.1) and (III.2), when two vicinal Z¹ to Z⁶ groups togetherform an electron-withdrawing or non-electron-withdrawing ring, said ringis other than the carbene L_(γ) of formula (II) and optionally hasheteroatoms selected from the group consisting of O, N and S.
 27. Thecomposition according to claim 14, wherein M is platinum in the zerooxidation state.
 28. The composition according to claim 15, wherein T₁or T₂ represents methyl, n-propyl, n-pentyl, cyclohexyl, adamantyl,allyl, methallyl, propargyl or homopropargyl.
 29. The compositionaccording to claim 18, wherein X in formula (IV.1) and (IV.2) is anoxygen atom.
 30. The composition according to claim 13, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 31. The composition according to claim 14, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 32. The composition according to claim 15, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 33. The composition according to claim 16, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 34. The composition according to claim 17, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 35. The composition according to claim 18, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4-y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2, or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 36. The composition according to claim 19, wherein the POSs-A- and —B— are chosen from those composed of siloxyl units of theformula:(R²⁰)_(x)SiO_((4-x)/2)   (I′) and/or of siloxyl units of the formula:(R²¹)_(y)(R²²)_(z)SiO_((4y-z)/2)   (II′) in which formulae the symbolshave the following meanings: R²⁰ and R²², which are identical ordifferent, each represent a group with a nonhydrolyzablehydrocarbonaceous nature which is: an alkyl or haloalkyl radical havingfrom 1 to 5 carbon atoms and having from 1 to 6 chlorine and/or fluorineatoms, a cycloalkyl or halocycloalkyl radical having from 3 to 8 carbonatoms and having from 1 to 4 chlorine and/or fluorine atoms, an aryl,alkylaryl or haloaryl radical having from 6 to 8 carbon atoms and havingfrom 1 to 4 chlorine and/or fluorine atoms, or a cyanoalkyl radicalhaving from 3 to 4 carbon atoms; R²¹ represents a hydrogen atom, a C₂-C₆alkenyl group, a hydroxyl group, a hydrolyzable atom or a hydrolyzablegroup, provided that when there are multiple R²¹ groups, they areidentical or different; x is an integer equal to 0, 1, 2,. or 3; y is aninteger equal to 0, 1, 2, or 3; z is an integer equal to 0, 1 or 2; andthe sum y+z is from 1 to 3 inclusive; with the condition that theSi-alkenyl POS -A- comprises at least one unit R²¹=alkenyl per moleculeand the Si—H POS —B— comprises at least one unit R²¹=hydrogen permolecule.
 37. A metal complex or catalyst comprising at least onecompound having the formula (I):

in which: M represents a metal of Group 8 of the Periodic Table; L_(γ)represents a carbene of formula (II):

in which: A and B, which are identical or different, represent C or N,it being understood that, when A represents N, then T₄ does notrepresent anything and, when B represents N, then T₃ does not representanything; T₃ and T₄ independently represent a hydrogen atom; an alkylgroup; a cycloalkyl group optionally substituted by alkyl or alkoxy; anaryl group optionally substituted by alkyl or alkoxy; an alkenyl group;an alkynyl group; or an arylalkyl group in which the aryl part isoptionally substituted by alkyl or alkoxy; or T₃ and T₄ can together andwith A and B, when the latter each represent a carbon atom, form anaryl; T₁ and T₂ independently represent an alkyl group; an alkyl groupoptionally substituted by alkyl; a perfluorinated alkyl group or analkyl group optionally substituted by a perfluoroalkyl group; acycloalkyl group optionally substituted by alkyl or alkoxy; an arylgroup optionally substituted by alkyl or alkoxy; an alkenyl group; analkynyl group; or an arylalkyl group in which the aryl part isoptionally substituted by alkyl or alkoxy; or T₁ and T₂ independentlyrepresent a monovalent radical of following formula (V):V₁-V₂   (V) in which: V₁ is a divalent hydrocarbonaceous radical, V₂ isa monovalent radical selected from the group consisting of the followingsubstituents: alkoxy, —OR^(o) wherein R^(o) is hydrogen, alkyl or aryl,and amine; T₁ and T₂ independently represent a monovalent radical offollowing formula (W):W₁-ω-W₂   (W) in which: W₁ is a divalent hydrocarbonaceous radical; ωrepresents: —R¹C═CR¹— wherein R¹ is H or alkyl, or—C≡C—; W₂ is a monovalent radical selected from the group consisting ofthe following substituents: R², which is alkyl or H; Si-alkyl orSi-alkoxy; alcohol; ketone; carboxyl; amide; and acyl; or thesubstituents T₁, T₂, T₃ and T₄ form in pairs, when they are situated attwo adjacent points in the formula (II), a saturated or unsaturatedhydrocarbonaceous chain; and with the condition that at least onesubstituent T₁ and/or T₂, which are identical or different, represent(s)a monovalent radical of following formula (V):Z₁-Z₂   (V) in which: Z₁ is a divalent hydrocarbonaceous radical, and Z₂is a monovalent radical selected from the group consisting of: a(C₅-C₃₀)cycloalkyl radical having at least one heteroatom in the ring,and a (C₆-C₃₀)aryl radical having at least one heteroatom in thearomatic ring, L_(α) and L_(β) are ligands which are identical to ordifferent from each other and each represent:

wherein, in these formulae (III.1) and (III.2): Z¹, Z², Z³, Z⁴, Z⁵ andZ⁶ each independently represent: hydrogen, halogen, cyano, or asaturated or unsaturated, electron-withdrawing ornon-electron-withdrawing, hydrocarbonaceous group, or two vicinal Z¹ toZ⁶ groups together form an electron-withdrawing ornon-electron-withdrawing ring which optionally comprises heteroatoms; orL_(α) and L_(β) together form the ligand L_(δ) of formula (IV):

in which: Y₁ and Y₂ represent, independently of each other, CR_(a)R_(b)or SiR_(c)R_(d); X represents O, NR_(e) or CR_(f)R_(g); R¹⁰, R¹¹, R¹³and R¹⁴, which are identical or different, are selected from the groupconsisting of a hydrogen atom, an alkyl group and an aryl groupoptionally substituted by alkyl; R⁹, R¹², R_(a), R_(b) and R_(e) areselected independently from the group consisting of a hydrogen atom; analkyl group; an acyl group; an aryl group optionally substituted byalkyl; a cycloalkyl group optionally substituted by alkyl; and anarylalkyl group in which the aryl part is optionally substituted byalkyl; R_(c) and R_(d) are selected independently from the groupconsisting of alkyl; aryl optionally substituted by alkyl; cycloalkyloptionally substituted by alkyl; and arylalkyl in which the aryl part isoptionally substituted by alkyl; or when Y₁ and Y₂ independentlyrepresent SiR_(c)R_(d), two R_(c) groups bonded to two separate siliconatoms together form a chain of the formula:

in which n is an integer from 1 to 3; X is as defined above; R and R′,which are identical or different, have any one of the meanings givenabove for R_(e), it being understood that, when n is 2 or 3, only onesilicon atom of the said chain may be substituted by one or two alkenylor alkynyl groups; or when Y₁ and Y₂ independently representSiR_(c)R_(d), two R_(c) groups bonded to separate silicon atoms togetherform a saturated hydrocarbonaceous chain, the two R_(c) groups forming,together with the said silicon atoms and X, a 6- to 10-membered ring; orwhen Y₁ and Y₂ independently represent CR_(a)R_(b), two R_(a) groupsbonded to separate carbon atoms together form a saturatedhydrocarbonaceous chain, the two R_(a) groups forming, together with thecarbon atoms which carry them and X, a 6- to 1 0-membered ring; andR_(f) and R_(g) represent, independently of each other, a hydrogen atom;an alkyl group; an acyl group; an aryl group optionally substituted byalkyl; a cycloalkyl group optionally substituted by alkyl; an arylalkylgroup in which the aryl part is optionally substituted by alkyl; ahalogen atom; an alkenyl group; an alkynyl group; or an SiG₁G₂G₃ groupwhere G₁, G₂ and G₃ are, independently of one another, alkyl; alkoxy;aryl optionally substituted by alkyl or alkoxy; or arylalkyl in whichthe aryl part is optionally substituted by alkyl or alkoxy.
 38. A metalcomplex or catalyst according to claim 37, wherein M is Pt, Pd or Ni inthe zero oxidation state.
 39. A metal complex according to claim 37,wherein L_(α) and L_(β) together form a ligand L_(δ) of formula (IV) inwhich Y₁ and Y₂ either both represent CR_(a)R_(b) or both representSiR_(c)R_(d), so that the complexes have the formula (IV.1) or theformula (IV.2):

wherein the two R_(a) groups, the two R_(b) groups, the two R_(c) groupsand the two R_(d) groups are identical to one another and R⁹═R¹²;R¹⁰═R¹⁴; and R¹¹═R¹³.
 40. A metal complex or catalyst according to claim37, having the formula (I.1):

in which: T₁ and T₂ are identical and are as defined in claim 37; T₃ andT₄ are as defined in claim 37; and and R_(c) and R_(d) are as defined inclaim
 37. 41. A process for the hydrosilylation of olefins or ofacetylenic derivatives, said process comprising heating a compositionaccording to claim 13 at about 100° C. or greater to crosslink its -A-and —B— polyorganosiloxane components.
 42. A process for thehydrosilylation of olefins or of acetylenic derivatives, said processcomprising heating at least one PolyOrganoSiloxane -A- (POS) carryingethylenic and/or acetylenic unsaturations and at least onepolyorganohydrosiloxane —B—, in the presence of a metal complex orcatalyst as defined in to claim 37 at about 100° C. or greater tocrosslink said -A- and —B— components.
 43. The process according toclaim 41, wherein the catalyst C in the composition comprises at leastone ligand L_(α) or L_(β) of formula (III.1) or (III.2).
 44. The processaccording to claim 41, wherein the composition comprises at least oneinhibitor -D- which is a ligand L_(α) or L_(β) of formula (III.1) or(III.2).